Centering device for well casings



Nov. 17, 1953 R. c. BAKER 2,659,439

CENTERI-NG DEVICE FOR WELL CASINGS Filed Dec. 27, 1949 15 14a r 7 v J 16 A 14 a. B 5 l M I, I 2/ i 12a g 4i I i 1 16 J L @5055 C BAKER,

INVENTOR.

#rraewsxs Patented Nov. 1?, 1953 2,659,439 CENTERING DEVICE FOR WELL CASIN GS Reuben C. Baker, Coalinga,

Calif., assignor to Baker Oil Tools, Inc, Vernon, C'alifl, a corporation of California Application December 27,

3 Claims.

The present invention relates to devices for maintaining casing, liner and similar conduit strings spaced from the walls of an encompassing well bore.

An object of the present invention is to provide an improved rigid well conduit centering device capable of positively maintaining an adequate clearance space between the conduit and the wall of the well bore containing the conduit.

Another object of the invention is to provide a rigid centering device for a well conduit that is strong and sturdy, despite the comparative lightness of the materials from which it is made, and which is also relatively economical to manufacture.

A further object of the invention is to provide a rigid centering device for well casing, and similar conduit, strings which tend to prevent channeling of cement slurry deposited behind the casing string.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings forming part of the present specification. It will now he described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation of a centering device mounted on a well bore;

Fig. 2 is a cross-section taken along the line 2-2 on Fig. 1;

Fig. 3 is a fragmentary longitudinal section taken along the line 3-3 on-Fig. 2;

Fig. 4 is an isometric projection of one of the rib members forming part of the centering device:

Fig. 5 is a top plan view of a blank from which one of the rib members is formed.

The device illustrated in the drawings is a rigid type of centering device A that can be mounted on or made to form part of a casing, liner or similar conduit string B disposed in a well bore C.

Such centering device maintains the conduit string spaced from the wall of the well bore, or in a comparatively centered position, particularly when the diameter of the well bore is substantially greater than the outside diameter of the casing string, or of its coupling collars.

casing string disposed in a relatively thin accompanying and 12.-

' portions i6, i6 projecting 1949, Serial No. 135,136

collars I 0, II are slzdable on the ceslne st in B, or they may be rigidly attached thereto, as desired.

The ribs are comparatively rigid and are designed to withstand lateral deformation in the event that the casing string leans against the formation wall with a comparatively great force.

sheet metal. In order to impart rigidity to the metal, it is formed into a generally channel shape, consisting of a mid-section l3 and tapered end sections Hi, It. The mid-section and end sections include a central web portion I5, which has a convex exterior, and in the same direction from the web portion [5, to produce a generally U-shape cross-sectional member, as disclosed most clearly in Fig. 2.

The end sections [4 are preferably tapered, with their terminal portions Ma snugly fitting the exterior of the collars it, H to which the ribs i2 may be permanently secured. as by the aid of a head of welding material I! that may run entirely around each collar, in order to integrate the end portions thereto.

The tapered end portions is may be made of any suitable length, for appropriately spacing the mid-sections l3 relative to the periphery of the casing string B, and thereby determine the eifeotive diameter of the centering device in holding the casing string spaced from the wall of Of course, the farther from the casing string the mid-sections 13 are placed. the larger is the diameter bore hole in which the device can be used efiectively.

Each channel or trou h-sha ed I2 may be formed from a sheet metal blank it, such as dis closed in Fig. 5. This blank a mid-portion i3 and end portions M between which generally V-shaped notches are provided. The corners 2d of the end portions 44 are beveled. so that such beveled members may lie flush a ainst the end collars id, H when. mounted thereon.

In order to form the trough-shaped member [2, such as illustrated in Fig. 4. the blank i8 bent enerally alon v the fold lines r in the direction, to form the channeled flanges id and web 5 for both the mid-section iii of the rib and its tapered end portions [4. The web portions 15 are also given the curved or arcuate configuration, while the bends about the lines 1' may also possess a radius to avoid sharp external corners. The end portions it are also bent along the fold lines s until the sides of the V-shaped notches i9 engage one another, which determines the extent of inclination of the tapered end portions M with respect to the mid-section is. The ends Ma of the blank. are also bent, so that their curvature conforms to the curvature of the collars id, H on which the ends Ma are to snugly engage, in order to insure a proper weld to the collars.

All of the foregoing bending and folding operations can talze place at the same time by providing a suitable forming die. The curvature of the webs :5, the bending of the flanges l5, and the bending of the tapered portions it about the fold lines 5, together with the proper curving of the terminals l lo of each rib to fit the collars i H, is performed by a single stroke of a die me nber towards its mating die member. In addition, the excess metal at the ends of the blank is trimmed off by a suitable shearing device after the rib {2 has been formed.

The mid-section and end section flanges it are then welded to one another along their abutting joints 2%, to integrate the flanges and to produce a rigid structure. The ribs l2 are then welded onto the end collars Hi, i l, completing a centering device.

The centering device A slid over the end of a casing section and may be firmly secured thereto, if desired, by means of welding material, or set screws (not shown), attaching one or both of the collars ii}, ii to the casing. If desired, a suitable stop ring (not shown) may be welded to the casing string B to one side of the centerdevicc, such ring engaging the centering device A and movin it through the well here with the casing string. For that matter, a casing c upli g collar itself (not shown) can function op member, forcing the centering device h the well bore.

lateral outward projection of the centervice causes its web portions to engage and hold the casing th o the wall of the well bore C, string properly spaced with respect to the well bore. The channel shape of each rib i2 makes it extremely rigid, since the flanges h; afford proper support to the formation wall engaging webs it. The inward thrust is transmitted from central web l5 to the flanges i of the midsection and through these flanges to the end flanges 5 which bear against the collars it, H. The weld i':, of course, prevents longitudinal dis placement of the ribs 2 with respect to the collars i8, H.

The provision of an adequate clearance space around the casing string insures that any cement slurry, or other oementitious material, deposited behind the casing Sb]. will be able to completely encompass the latter, oifering far better chance for a succes ful cementing job. In addition, the circumferentially spaced ribs i2 form ba-I'lles or restrictions for the cement slurry, and cause it to deviate laterall around the casing string for upward passage along the casing string between the l2, or produce acceleration of the slurry between the ribs and the formation wall. Such lateral deviations and accelerations tend to prevent channeling of the cement slurry,

offer greater assurance for the circumferential continuity of the cementitious seal.

If desired a duplicate centering arrangement can be used, as disclosed in Fig. 1. With this arrangement. another set of ribs 520., as a lower set, are longitudinally spaced with respect to a single set of ribs 12, such as an upper set. The lower collar H for the upper set of ribs may be elongated to enable the upper ends of the lower ribs l2a to be welded thereto. The lower ends of these last-mentioned ribs may be welded to a lower collar or ring 30.

The lower set of ribs :20. is angularly displaced with respect to the upper set 12. Assuming that each set has three ribs, and that each rib extends about sixty degrees around the casing string, the lower set may be displaced about sixty degrees with respect to the upper set. As a result of this arrangement, the upper and lower sets of ribs l2, 12a together provide about a 360 degree contact surface with the formation wall, increasing the capacity of the centering device, and insuring that the web portions 15 of the ribs will have adequate bearing against the formation wall, regardless of the lateral direction in which the casing string B tends to lean against the formation wall.

Not only does the staggered arrangement of the two sets of ribs l2, lZa increase the load carr ing capacity of the device considerably, but it also forms a tortuous path for the cement slurry during its upward travel around the casing string. Such slurry will pass upwardly between the ribs 120. of the lower set, but must then move arcuately, in order to pass between the ribs ii of the upper set. This staggered arrangement also minimizes the chance of channeling of the cement slurry, and enhances the obtaining of the circumferentially continuous cementitious seal around the casing string.

It is, accordingly, apparent that centering devices have been provided which can be manufactured in a comparatively economical manner, and in which light materials are availed of to provide a strong and sturdy construction. The arrangement is such as to keep the casing adequately displaced from the wall of the well bore around the entire circumference of the casing, the centering ribs themselves minimizing the tendency for the cement slurry to channel. while being displaced behind the casing.

The inventor claims:

1.1n a centering device for a well conduit string: upper and lower longitudinally spaced circumierentially continuous cylindrical collars having cylindrical peripheries; and a plurality of circumferentially spaced ribs extending between said collars; each rib having an out"- ardly facing web of substantially uniform thickness including a medial portion and end portions topered toward and secured to the peripheries of said collars, each rib also having medial and end flanges secured to and extending in substantially parallel relationship inwardly from said medial and end web portions, said medial and end rage; at each longitudinal edge of said web poi ions being substantially coplanar, angled with respect to each other and welded to each other, the inner ends of said end flanges bearing against said cylindrical peripheries.

2.111 a centering device for a well conduit string: upper and lower longitudinally spaced circumferentially continuous cylindrical collars having cylindrical peripheries; and a plurality of ciroumferentially spaced ribs extending between said collars; each rib being of one piece of sheet metal of substantially uniform thickness and having an outwardly facing web includ ing a medial portion and end portions tapered toward and secured to the peripheries of said collars, each rib also having medial and end flanges extending substantially normally inwardly from the sides of said medial and end web portions, said medial and end flanges on each side of said web portions being substantially coplanar, angled with respect to each other and welded to each other, the inner ends of said end flanges bearing against said cylindrical peripheries.

3. In a centering device for a well conduit string: upper, intermediate and lower longitudinally spaced circumferentially continuous cylindrical collars; an upper set of circumferentially spaced rigid ribs extending between and secured to said upper and intermediate collars; a lower set of circumferentially spaced rigid ribs extending between and secured to said intermediate and lower collars; said sets of ribs being circumferentially offset with respect to each other; each rib being of one piece of sheet metal of substantially uniform thickness and having an out- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,860,659 Criley May 31, 1932 2,156,644 Thomasen May 2, 1939 2,157,493 Miller et a1 May 9 1939 20 2,482,985 Lockwood Sept. 27, 1949 

